It should be quite fast on that system. Keep in mind simulation games are not designed to hit 60fps, so 25-35fps is the range you are likely to see.

To get better fps make sure you do not enabled bloom, set water no higher than low 2.x, turn all the traffic sliders down to zero, and set autogen at dense. Pretty much everything else can be maxed out, though I keep coud draw distance at 80 miles.

This gives the best balance between performance and visual quality for me, and on my system its fast enough for me to take water up to high 2.x, and autogen up to very dense, though I keep traffic down being I do not interact with it at all.